Method of driving propellers and rotative wing systems



Sept. 5, 1933. 1,925,156

METHOD opmuvme PROPELLERS AND ROTATIVE wme SYSTEMS V S. P. VAUGHN FiledAug. 26, 1930 2 Sheets-Sheet l Sept. 5, 1933. s. P. VAUGHN 1,925,156

METHOD OF DRIVING PROPELLERS AND ROTATIVE WING SYSTEMS Filed Aug. 26,1950 2 sheets-sheet 2 Patented Sept. 5, 1933 UNITED STATES lVIETHOD OFDRIVING PROPELLERS AND ,ROTATIVE WING SYSTEMS Sidney P. Vaughn, UnitedStates Navy, Ackerman, Miss.

Application August 26, 1930. Serial No. 477,842

22 Claims.

(Granted under the Act of March 3, 1883, as amended April 30, 1928; 370O. G. 757) This invention relates to a method of driving propellers androtative wing systems, and while it is intended for air vehicles theprinciples may be applied in driving other types of vehicles and boats.This invention includes also a rotative hinged wing system incorporatingthe method of drive and which is particularly suited for sustainingaircraft of the helicopter type.

In order to simplify these specifications the term propeller is intendedto include rotating wing systems for sustaining vehicles of the air, andpropellers or air screws for propelling vehicles of the air as well asother types of vehicles and boats. The term impeller is intended toinclude blower impellers, propeller fans and centrifugal fans, forcreating a blast of air.

It is well known that the larger the diameter of a propeller the greaterwill be the thrust per horse power developed by the prime mover drivingthe propeller, but in view of the high speeds of present day internalcombustion engines and the future probable increase in the speeds ofsuch engines, it is the practice to introduce a reduction gear betweenthe propeller-and the prime mover in order to obtain higherefiiciencies. Even this is not satisfactory where the speed ratio be-:tween the prime mover and the propeller is very high due to the largesize of the reduction gear and abnormal strains caused by unequal orsudden acceleration or deceleration of the prime mover and to varyingair currents through which the aircraft flies.

The principal object of this invent-ion is to avoid the use of heavydrive shafts, mechanical clutches. reduction gears, and belt drives indriving propellers of large diameter, by driving the propeller throughthe medium of what may be termed an air clutch, which in its simplestform, comprises a windmill or air turbine coni nected to, the propellerand an air impeller driven by a prime mover, the two being so disposedwith relation to each other that an air stream produced by the impellerdrives the windmill or air turbine which in turn drives the propeller.With this method of drive an impeller having a low moment of inertia maybe driven at a high speed to produce a high velocity air blast to drivethe windmill or turbine. Due to the elasticity of the air, any abnormaltorque strains will not be transmitted from the prime mover to thepropeller nor from the propeller to the prime mover.

A further object is to utilize the reaction of the air stream dischargedfrom the windmill or air turbine described above to create a thrust inthe direction of the thrust of the propeller to increase the efiiciencyof the air clutch.

A further object is to make the air clutch" very compact, light andefiicient by mounting the windmill or air turbine on the same shaft oraxis of the impeller and closely adjacent to the impeller, so that itwill rotate freely on the impeller shaft in the air. stream produced bythe impeller.

A further object is to include in the structure of a propeller blade,windmill or air turbine blades to drive the propeller blades when actedupon by ahigh velocity airstream produced by an impeller driven by aprime mover.

Another object is to provide in a freely rotative wing system having twoor more wings articulated to a common hub, and adapted to be driven bythe action of an air stream on windmill or turbine blades included inthe structure of the wings, means whereby the pitch of the wings, whenrotating in a lateral wind, is automatically changed to equalize thethrust of all wings, and means whereby the wings attain automatically apositive pitch when a torque is applied to the rotative wing system anda negative pitch when the torque is removed so that the wing system maycontinue to revolve as a windmill when sustaining aircraft.

Another object is to provide a propelling system for aircraft whereinfor a given torque and R. P. M. of the engine the thrust of thepropeller will remain a constant as the speed of the aircraft increases,and for all altitudes when the speed of the aircraft is increased due toa decrease in the density of the air. I

These and other objects and advantages as will hereinafter appear willnow be described with reference to the accompanying drawings in which:

Fig. 1 illustrates a plan view of the rotative wing system havingarticulated wings and shows the method of driving the wing system. Fig.2 illustrates a sectional elevation of the hub of the rotative wingsystem. Fig. 3 is a sectional elevation through the wing system lookingtoward the hub and showing the flow of the air stream through thedriving system. Fig. 4 is a sectional elevation of 1. Fig. 5 is a planview of a modified form of rotative wing. Fig. 6 is a plan view ofanother modified form of rotative wing. Fig. '7 is a perspective view insection showing a preferred form of air clutch for driving propellers.Fig. 8 is a perspective view insection showing a modified form of airclutch for driving propellers.

Like numerals refer to like parts throughout the several views:

One method of driving a freely rotative hinged wing system or propellersuitable for sustaining in flight aircraft of the helicopter type isillustrated in Figs. 1, 2, 3 and 4, in which numeral 1 represents thebody of a helicopter which is provided with a sustaining and propellingsystem comprising two or more blades 2, each of which is universallyconnected at its root end by a ball and socket joint 3 to a common hub 4which rotates freely on an impeller drive shaft 5 beneath an impeller 6,attached securely to the upper end of the drive shaft 5, which is drivenby a prime mover or engine 7 attached to the body of the helicopter. Theball and socket joint 3 permits each blade to articulate in anydirection and to rotate around its longitudinal axis X. The

downward movement of the blades is restricted by cables 8 and springs 11connecting the outer portion of each blade to a common ring 9 whichrotates freely on a king post 10 formed by an upward extension of thedrive shaft 5. The upward movement of the blade, and its rotativemovement, is restricted by a depending arm 12, attached to the root endof the blade spar 13, making contact with stops 14 attached to the baseof the propeller hub 4. The degree of rotation each blade is permittedto make around its longitudinal axis X is fixed bythe difference indegrees of are between the positive and negative pitch angles desired inthe blades to produce best results. The lateral movement of each bladein its plane of rotation relative to the hub is limited by the amount ofgive in the cables 15 and springs 16 which connect the blades to eachother in the plane of rotation. This arrangement makes the rotative wingsystem or propeller very flexible which is essential as will be morefully explained.

An airfoil shaped windmill or driving blade 17, suitably disposed in theair stream of 'the air impeller 6, is adjustably fixed to the root endof each propeller blade spar 13 with its longitudinal axis parallel tothe longitudinal axis of the propeller blade 2 and its cord or drivingface set at such an angle with reference to the air stream of theimpeller 6 as to apply the maximum torque to each propeller blade whenacted upon by an' air stream produced by the impeller. Since the drivingblade 17 and the propeller blade 2 are fixed to a common spar 13 bothwill revolve around the same longitudinal axis, and a decrease in'thepitch of the propeller blade 2 with reference to the plane of rotationwill cause an increase in the pitch of the driving blade 17 withreference to the air stream flow from the impeller. Conversely, anincrease in the pitch of the propeller blade will cause a decrease inthe pitch of the driving blade. If the center of pressure (circle c.p.)on both the propeller blade 2 and the driving blade 17 is located to therear of their common longitudinal axis, and increase in the velocity ofthe impeller air stream will cause a corresponding increase in pressureon the driving blade 17 which will cause the driving blade and thepropeller blade to rotate downward until the pitch of the propeller issuch that the upward pressure or thrust when rotating will balance thedownward pressure acting upon the driving blade. Conversely, if theupward thrust of the propeller blade is increased over the downwardpressure acting upon the driving blade, the pitch of the propeller bladerelative to its plane of rotation will decrease and the pitch of thedriving blade relative to the flow of the air stream from theimpellerwill increase until both pressures balance. This feature is particularlydesirable to equalize the lift on all blades when the propeller isrotating in a lateral wind. It is well known that when propeller bladesare fixed to the hub and are rotating in a lateral wind, that the bladeadvancing into the wind will have a greater thrust than the bladereceding from the wind, which is a condition not desired in a propelleradapted to sustain a helicopter if the helicopter is to remain stable.

If the propeller blades are articulated as described herein and theweights along their longitudinal axis are properly disposed, they will,dur-.

above the plane of rotationfas indicated by the dotted axial line X inFig. 4.

The torque applied to each propeller blade by its driving blade may begreatly increased if the driving blade is made in the form of what isknown as the slotted wing. In this invention this is accomplished byspacing a small airfoil section 18 over the leading edge of the drivingblade 1'7 to act as an air deflector which turns the lines of air flow;along the back surface of the driving blade, thus resisting the collapseof the flow which is characteristic of an airfoil without the slot atvery large angles of attack. The introduction of a-slotin the drivingblade therefore makes it possible to increase the angle of attack of thedriving blade with a consequent increase in the torque driving thepropeller blade.

Should for any reason during flight, the impeller 6 stops or its speedslows to an idling speed, the downward thrust on the driving blades 17decreases and the upward thrust on the propeller blades 2 causes theblades to attain a negablades 17 at a very large angle of attack whichidling speed the downward pressure on the driv-' ing blade 17 is reducedand the upward thrust on the propeller blade, which will be rotating,and the pressure of the lateral wind, indicated by the heavy arrow fW,against the back of the driving blade, causes both blades to rotateclockwise, looking toward the hub, and the propeller blade to attain anegative pitch as indicated by the pitch line 2-b and the driving bladeto attain a pitch indicated by the pitch line 17-12.

In the foregoing description the driving blade 17 has been shown as asingle blade, but it will be understoodthat it may take any form, or,that two or more driving blades may be used to drive the propeller bladeas indicated in Figs.

5 and 6. In Fig. 5 is illustrated a propeller blade 2 in which fourdriving blades 1'! are provided in the structure of the propeller blade2. In Fig. 6 the propeller blade 2 and the driving blade 17 are shown asa single unit with the cord face of the driving blade 17 on the sameside of their common longitudinal axis X as the cambered the propellerblade.

Another type of air clutch for driving propellers is illustrated in Fig.7, in which a multi bladed fan wheel 24 provided with radial blades ofshallow depth and concave with concave surface forward in rotation, isconnected to a prime mover through a drive shaft 5. A turbine wheel 23provided with curved radial blades of shallow depth with concave surfacerearward in rotation is mounted to rotate freely on the drive shaft 5,beneath the fan wheel 24, with its radial blades encircling the fanwheel blades and disposed in the tangential flow of the air streamproduced by the fan wheel when rotating. In order that the energy in theair stream may be utilized to the fullest, an annular deflector 25encircling the turbine blades is provided to deflect the air stream in adirection opposite to the thrust of the pro back of peller blades 2driven by the turbine. The flow of the air stream through the turbine isindicated by the dotted lines (2 and the direction of rotation of thefan wheel and the turbine is indicated by the arrows. The abovearrangement makes a very compact and efficient form of air clutch fordriving propellers of large diameter with small high speed engines wherethe speed ratio is so great that a reduction gear is impracticabie. I

Another modification of theair clutch is illustrated in Fig. 8, in whicha propeller fan 6 drives a windmill 20 having curved blades 21 with theconcave side so disposed as to receive the impact of the air streamproduced by the propeller fan 6. The windmill in turn drives two or morepropeller blades 2 hinged to an annular ring secured to-the outer endsof the blades. Instead of mounting the windmill directly on the shaft ofthe propeller fan it may be mounted to rotate freely on a tubular member22, connected to the body of the aircraft 1, through which passes thedrive shaft 5 connecting the propeller fan 6 to the prime mover whichmay be located in the body of the aircraft. This type of air clutchoperates in the same manner as the one illustrated in Fig. 7, in thatthe propeller 2 may be driven at a slow speed by a high speed enginewithout the use of reduction gears.

It has been shown by several investigators that for a given torque andR. P. M. the thrust of a propeller rotating in a lateral wind increaseswith the velocity of the lateral wind. It is this property that isutilized to the fullest throughout this invention. In the method ofdriving a sustaining air screw or rotating wing system as illustrated inFigs. 1, 2, 3, and 4, both the impeller and the propeller are adapted torotate in a lateral wind. As the velocity of the lateral wind increasesthe thrust of the impeller and the propeller increases,

which means that the mass of air passing through the impeller blades andimpinging upon the driving blades of the propeller has increased whichautomatically increases the torque on the propeller. This together withthe auto-giro effect on the propeller bladescauses them to rotate muchfaster than they would normally rotate if there were no lateral wind.This is a very desirable feature when the propeller is used to sustainaircraft of the helicopter type where.the sustaining effort should beuniform for all transitional speeds as well as for all altitudes and airdensities. In other words, when the sustaining system is driven in themanner shown, that is, with an air clutch, the ratio between the upwardthrust of the sustaining propeller and a given engine torque will beuniform for all transitional speeds and altitudes.

When a propeller is used to propel an airplane I through the air in themanner now common, that is, with the propeller connected directly to theshaft of the engine, the thrust of the propeller decreases with theforward movement of the airplane. As a result, in order to keep theengine from racing, it isnecessary to throttle down, or else increasethe pitch of the propeller blades in order to keep the thrust and torqueconstant. Since the most efiicient pitch of the blades is that whichwill give the highest Lc/Dc for any particular section of the blade, itis evident that the pitch of the blades cannot be changed to compensatefor the variations in thrust, without lowering their efiiciency. Inorder to keep the propeller thrust a constant it is necessary that thespeed of the propeller be increased in proportion to the speed of theairplane. Since the speed of the engine is limited, the only way thatthe speed of the propeller may be increased is by using an air clutch,such as described herein and illustrated in Fig. 7, or by using ahydraulic clutch, wherethe ratio between the speed of the engine and thespeed of the propeller may be a variable.

In using a hydraulic clutch where the speed ratio is high the efllciencyof the clutch would be very low, but if an air clutch, such asillustrated in Fig. 7, the efliciencyfor all speed ratios would be veryhigh due to the fact that the reaction from the air passing through theclutch is in the same direction as the thrust of the' propeller. If atractor propeller is driven by an air clutch such as is illustrated inFig. '7, the mass of air passing through the clutch will increase withthe forward speed of the airplane, causing the speed of the engine toremain a constant and the speed of the propeller to increase and itsthrust to remain a constant.

With the ordinary type of airplane where the propeller is connecteddirectly to the drive shaft of the engine, such as in use today, theresistance to forward movement decreases with altitude and a reductionin the density of the air, but, due to the fact that the speed of theengine cannot be increased beyond its designed maximum speed, nor thepitch of the propeller be increased to operate efficiently, an'altitudeis soon reached where the speed of the airplane cannot be increased andthe lift and gravity forces balance. By using an air clutch such as thatdescribed herein and illustrated in Fig. '7, where the thrust andhorsepower ratio remains a constant, the altitude that may be attainedby an airplane and its speed at those altitudes will be limited only bythe mechanical devices supplying the engine with oxygen and the abilityof the metals in the propeller to withstand centrifugal forces.

Instead of including the clutch in the propeller structure in the mannerillustrated, it may be advisable at times. to placethe clutch in theshaft system and entirely separated from the engine and propeller exceptthrough the drive shafts.

It will be understood that I may modify the air clutch construction inmany ways without departing from the principles of the invention and thespirit of the following claims.

l claimz 1. In a rotative wing system, a shaft, a hub mounted on saidshaft and freely rotatable thereon, aerofoils pivotally attached to saidhub, impellersmounted between said aerofoils and said hub, a propellersecured to said shaft, a prime mover for driving said shaft andpropeller thereby producing an air flow to drive said impellers torotate the aerofoil.

2. In a rotative wing system, a shaft having bearings positionedthereon, a hub mounted between said bearings and free to rotate uponsaid shaft, aerofoils pivotally attached to said hub, impellersintegrally connected with said aerofoils, a prime mover for driving saidshaft, and a propeller secured to said shaft for directing an air streamagainst said impellers to rotate the airfoils.

3. In a helicopter, in combination, a body, a prime mover supported bysaid body, a shaft driven by said prime mover, a propeller secured tosaid shaft for generating an air blast, a hub free to rotate on saidshaft, bearings on said hub, aerofoils pivotally connected to said hubbearings, and means for driving said aerofoils by the air blastgenerated by said propeller.

4. In a helicopter, in combination, a body, a-

prime mover supported by said body, a shaft driven by said prime mover,a propeller secured to said shaft for generating an air blast, a hubfreely rotatable on said shaft, aerofoils pivotally connected to saidhub, impellers supported by said aerofoils and driven by the air blastof said propeller.

5. In a helicopter, in combination, a body, a prime mover, a shaftdriven by said prime mover, a propeller secured to said shaft forgenerating an air blast, a hub freely rotatable on said shaft, aerofoilspivotally connected to said hub, and means integral with said aerofoilsand interposed between said prime mover and said. propeller for drivingsaid aerofoils by air blast from said propeller.

6. In a helicopter, in combination, a body, a prime mover supported bysaid body, a shaft driven by said prime mover, a propeller secured tosaid shaft for generating an air blast, a hub freely rotatable on saidshaft, aerofoils pivotally connected to said hub, means surrounding saidshaft and impellers having means thereon to direct the air flow,interposed between said prime mover and said propeller for driving theairfoils by the air blast of the propeller.

7. In a helicopter, in combination, a body, a prime mover supported bysaid body, a shaft driven by said prime mover, a propeller secured tosaid shaft for producing an air blast, a. hub freely rotatable on saidshaft, thrust hearings on said shaft for locating said hub, hearings onsaid hub, aerofoils pivotally connected to the bearings on said hub,damping means between said aerofoil and said shaft for limiting the downmovement of the said aerofoils, stops carried by said aerofoils forlimiting angular up movement of said aerofoils, impeller bladessupported by said aerofoils for imparting rotary motion from saidpropeller air blast, means for varying the pitch of the aerofoilsautomatically due to forward translation.

8. In a helicopter, in combination, a body, a

'prime mover supported by said body, ashaft driven by said prime mover,a. propeller secured to said shaft for producing an air blast, a hubfreely rotatable on said shaft, thrust bearings on said shaft forlocating said hub, bearingsv on said hub,

aerofoils pivotally connected to the hearings on said hub, damping meansbetween said aerofoil and said shaft for limiting the down movement ofthe said aerofoils, stops carried by said aerofoils for limiting angularup movement of said aerofoils, impeller blades supported by saidaerofoils for imparting rotary motion from said propeller air blast,means for equalizing torque of each of. said aerofoils automatically asangle of incidence of its respective blade of said impeller varies dueto driving energy.

9. In a helicopter, in combination, a body, a prime mover supported bysaid body, a shaft driven by said prime mover, a propeller secured tosaid shaft for producing an air blast, a hub freely rotatable on saidshaft, thrust hearings on said shaft for locating said hub, bearings onsaid hub, aerofoils pivotally connected to the bearings on said hub,damping means between said aerofoil and said shaft for limiting the downmovement of the said airfoils, stops carried by said aerofoils forlimiting angular up movement of said aerofoils, impeller bladessupported by said aerofoils for imparting rotary motion from saidpropeller air blast, means for decreasing the angles of incidence ofeach of said aerofoils when advancing into the wind due to forwardtranslation and increasing the angle of incidence of the said aerofoilswhile receding from the direction of forward translation.

10. In a helicopter, in combination, a body, a prime mover supported bysaid body, a shaft driven by said prime mover, a propeller secured tosaid shaft for producing an air blast, a hub freely rotatable on saidshaft, thrust bearings on said shaft for locating said hub, hearings onsaid hub, aerofoils pivotally connected to the bearings on said hub,damping means between said aerofoil and said shaft for limiting the downmovement of the said aerofoils, stops carried by said aerofoils forlimiting angular up movement of said aerofoils, impeller bladessupported by said aerofoils for imparting rotary motion from saidpropeller air blast, and means consisting of in tegrally mounting eachof said aerofoils and impeller whereby the variance of one changes theother.

11. In a rotative wing system for aircraft, combination, a prime mover,a shaft driven by said prime mover, a propeller secured to said shaftfor generating an air blast downwardly, a support for said prime moverhaving a bearing for said shaft, a. hub freely mounted to rotate on saidshaft, aerofoils pivotally attached to saidhub between said propellerand said prime mover, and impeller blades connected between saidaerofoils and the pivotal connection of said aerofoil to said hub forreceiving the air blast from said propeller for causing rotation of saidaerofoils.

12. In a rotative wing system for aircraft, in combination, a primemover, a shaft driven by said prime mover, a propeller secured to saidshaft for generating an air blast downwardly, a support for said primemover having a. hearing for said shaft, a hub freely mounted on saidshaft, aerofoils pivotally attached to said hub between said propellerand said prime mover, and

impeller blades integrally connected to said aerofoils in the samehorizontal plane and in line of the downward air blast of said propellerfor causing the 'rotation of said aerofoils.

13. In a rotating wing for aircraft, a plurality of aerofoils, liftingsections outboard and air driven impeller sections inboard in horizontalalignment with said lifting sections, and means sections, and means forwhereby each of the aerofoils is capable of oscillatory movement abouttheir common axes during rotary motion of the aerofoils.

15. In a rotating wing for aircraft, a plurality of aerofoils havinglifting sections outboard and air driven impeller sections inboardintegrally connected in horizontal alignment with said lifting sections,said impeller sections composed of a plurality of small inverted slotforming aero-' foil sections adapted to drive said aerofoils' by a blastof air directed against the impeller sections, and means for wherebyeach of the aerofoils about their common axes of rotary motion of theaerofoils is capable of oscillatory movement.

16. In a rotating Wing for aircraft, a plurality of aerofoils, pivotalconnects inboard, lifting sections outboard, and inverted impellersections between said pivotal connection and said lifting sections inhorizontal alignment therewith, and means for whereby each of theaerofoils is capable of oscillatory movement about said pivotalconnections.

17. In a rotating wing for aircraft, in combination, a plurality ofaerofoils, pivotal connections inboard, an area outboard comprisinglifting sections, areas inboard consisting of a plurality of smallinverted slot forming aerofoil sections in horizontal alignment with andadapted to drive said area outboard by a blast of air directed from thecenter of rotation of the blade from above the area inboard of theblade, and means for whereby the said aerofoils is capable ofoscillatory movement about said pivotal connections.

18. In a rotating lifting wing for aircraft pro pulsion, in combination,an area outboard of truev lift section, an area inboard consisting of aplurality of inverted slot forming impeller sections integrallyconnected in horizontal alignment and adapted to drive said areaoutboard by a blast of air from above.

19. In a rotating lifting wing for aircraft propulsion, in combination,a blade having a pivotal connection inboard, an area outboard of trueaerofoil lifting section, and an area inboardbetween the lifting sectionand the pivotal connection integrally connected and in horizontalalignment with the area outboard consisting of a plurality of invertedradial blades of shallow depth and concave in section and adapted todrive said blade by a blast of air directed from above said areainboard.

20. In a fan blade, in combination, an outer 21. In a. fan blade, incombination, an outerarea having a positive camber in cross section, anarm for attachment to a common hub inboard, an inner area having apluralityof inverted radial blades of shallow depth and concave in crosssection integral with and in horizontal alignment with the said areaoutboard, and means above the common hub of said arm for generating anair blast upon said area inboard for imparting rotary motion to the fanblades.

22. In a rotating fan system, in combination, a plurality of blades, anouter area having a positive camberv in cross section,'an arm forattachment to a common-hub inboard, an inner area having a plurality ofradial blades of shallow depth and concave in cross section integrallyformed with and in horizontal alignment with said area outboard, and aprime mover having a shaft forming a bearing for the free rotarymovement of the common hub of said arm and for driving a propellersecured to the shaft of said prime mover for directing an air blastdownwardly upon said inner area thereby driving the blades constitutingsaid outer area.

SIDNEY P. VAUGHN.

